Recently I was reading about extending jQuery's functionality and plugin system. I wrote two articles on extending jQuery functionality with your own custom functions. To extend you write $.fn.myFunction and then your function. It was interesting what $.fn is, so I look through the jQuery code and on line 33 found:
jQuery.fn = jQuery.prototype = { So jQuery's fn is just a synonym for its prototype. I know this is not a discovery of the century but it gives you some understanding of how jQuery's plug-in system works and its insights.